Nethertale
by Sass-Bot
Summary: When Papyrus naively trusts a stranger, he finds himself trapped in a completely different world -the Netherworld. Strangely enough, they folks there seem to like puzzles just as much as the folks back in the Underground. Meanwhile, Sans, fearing the worst, sets off to find his kid brother and realizes that things aren't always as black and white as they seem.
1. Year 210X

_"_ _Long ago, two races ruled over Earth:_

 _HUMANS and MONSTERS…_

 _One day, war broke out between the two races._

 _Countless monster SOULS were destroyed._

 _After a long battle, the humans were victorious._

 _They sealed the monsters underground with a magic spell._

 _The OTHERS were sealed elsewhere._

 _Neither monster, nor human…_

 _There was no place for them anymore. "_

* * *

"AGAIN!" Papyrus declared from down on the ground after being defeated again. He waved a bony finger at his adversary. "I WANT A REMATCH." He was significantly shorter than his opponent, yet he spoke with such conviction.

Undyne wiped the sweat off her brow and sighed heavily. This one wasn't a quitter, she noted with a smirk, drawing her spear into position and bracing herself. "You got it!" she called out, barely giving him the time to get back up on his feet before one of her spears was lodged into the snow beside him. She couldn't deny the fact that she was enjoying this immensely; she only hoped that she wouldn't freeze her scales off in the eternally snowy Snowdin Town.

She could feel a chill in her soul as Papyrus attempted his blue attack on her, and got ready to dodge a barrage of hits. She grinned in pride as she leaped and dodged, tossing up the snow under her boots as she did so. That blue attack had come quite far in the time that they'd been practicing together, and she wouldn't have been surprised if she found out that he'd been forgoing sleep in order to practice day and night. Of course, monsters didn't really _need_ sleep, but it was a nice way to recharge. Someone who was perpetually fully charged like Papyrus probably wouldn't need it though…

When the attack subsided, she flicked her crimson bangs away from her eyes and planted her feet firmly on the ground, thrusting her spear out dramatically. "That the best you got?" she challenged, hoping for another heart-pounding, blood-pumping blue attack.

"... ACTUALLY. YES… YES, IT IS," he replied flatly."I THINK IT WOULD BE BEST TO END OUR TRAINING SESSION NOW." His expression sunk slightly before he looked up again at Undyne with determination in his eye-sockets. "HOWEVER! THIS IS NOT THE LAST YOU'VE SEEN OF ME. I, THE GREAT PAPYRUS, WILL BE BACK… STRONGER THAN I WAS TODAY. PROBABLY."

She couldn't help but chuckle at him as she sheathed her spear. "That was such a thrilling fight! I can't wait until our next meeting!"

"ME NEITHER!" he replied, feeling his chest swell up in excitement. "WHEN ARE YOU FREE? TUESDAY?" Before giving Undyne a chance to reply, he spoke again. "NO. ACTUALLY TUESDAY I PROMISED SANS I WOULD PET-SIT OUR ROCK WHILE HE'S OUT… MAYBE DEFINITELY WITHIN THE NEXT WEEK," he told her with certainty. "IF NOT THEN, MAYBE THE WEEK AFTER FOR SURE."

She frowned slightly. "That's not very specific. Maybe you should call me when you're sure."

Papyrus nodded. "YES. I SUPPOSE THAT MAKES SENSE." He rose up from his couch, taking his and Undyne's joysticks with him, and turned off the video game console. "PERHAPS NEXT TIME, YOU COULD TRAIN ME TO FIGHT FOR REAL."

Undyne cocked her head to the side in thought. "For real?"

"YES. I WANT TO BECOME A ROYAL GUARD," he admitted, scratching the top of his skull and blushing. "THAT WAY I CAN BE COOL AND POPULAR LIKE YOU, UNDYNE."

"You sure about that? It's pretty boring work, being a Royal Guard; it's been awhile since a human came down here," she warned him, twirling a strand of her hair as she spoke. "Plus they've got me mostly doing grunt work…"

"WHAT?! YOU NEVER DO ANYTHING BORING! EVER! YOU TRAIN WITH THE KING EVERYDAY AND HAVE TONS OF ADORING FANS." Well, most of those fans were just Papyrus in different costumes, but still… "BESIDES, I CAN USE THE TIME SPENT WAITING FOR HUMANS TO PRACTICE MY HUMAN-CAPTURING SKILLS! NYEHEHEHEH!"

Undyne huffed, trying to hide her emotions from the easily manipulated Papyrus. "I guess, I _could_ help you out. But it will take hours -no, _days_ -maybe even _weeks_ of rigorous training."

"I CAN DO IT!"

"Well, then…Our next training session will be at my house over in Waterfall. Got it? And don't be late!" she ordered, sounding more like a drill sergeant than someone Papyrus had just been playing video games with.

With that, Undyne was gone and Papyrus was alone again. He walked into the kitchen and found a quiche made entirely of ketchup and bread sitting on the table -Sans's favorite. He cut out a slice for himself and began to eat. Curiously, he began to ponder how this was even possible. He didn't have internal organs -let alone a tongue… or an esophagus… or a stomach. Where did it go?

"hey." a familiar voice greeted. "you look like you're thinking real hard about something, kiddo."

"SANS! OH MY GOD!" Papyrus exclaimed loudly, slamming his fork down onto the table. "HOW DO SKELETONS EAT FOOD?"

"with a fork… and a spoon," Sans replied dryly, giving his brother the usual sly grin.

"SANS!" Papyrus scolded. "I WAS BEING SERIOUS"

He didn't even miss a beat saying, "and i was being humerus"

"..."

"..."

Papyrus saw that one coming, but he couldn't stop the frustrated groan that came out of him. "SAAANS!"

"guess that one didn't tickle your… funny bone… did it?"

"THAT ONE WAS EVEN LESS FUNNY THAN THE LAST ONE."

"it's an off day," he told his brother, his words surprisingly devoid of jokes. "i just realized i don't have internal organs, or a tongue, or an esophagus, or a stomach." He grinned like this knowledge didn't phase him in the least, unlike his mortified younger sibling.

* papyrus looked down at his food, suddenly unable to _stomach_ the concoction on his plate -

"SANS! STOP NARRATING MY ACTIONS WITH YOUR PUNS!"

"sorry." He didn't look sorry.

Papyrus got up from his seat, and Sans silently noted that his height was catching up to his older brother's; soon Papyrus would be taller than him. He only hoped that even then, Papyrus would continue to be the great kid that he was.

"CAN WE GO TO HOTLAND TODAY?" Papyrus asked, nearly hopping up and down on the tips of his phalanges.

Sans sighed and rubbed the top of his skull; he couldn't say no to that face. "hotland, eh?" he asked. "i heard things have been pretty quiet there since the queen left."

"LEFT?!" This was news to Papyrus, whose eyes would have widened had he had any skin. The queen had departed long before Papyrus was old enough to know much about her, and afterwards, King Asgore's ex-wife was a topic that few had the nerve to mention. "WHERE DID SHE GO?"

"nobody knows. she just disappeared."

"DID THE HUMANS TAKE HER AWAY?" he pressed, his tone imbued with concern for this monster he had neither seen nor met. "IS THAT WHY KING FLUFFYBUNS DOESN'T LIKE HUMANS?"

Unsure of how to answer that question without drudging up decades worth of painful history, Sans changed the topic. "say... didn't you wanna go to hotland?"

* * *

Hotland was particularly sweltering this time of year -or perhaps particularly sweltering in comparison to the frozen climate back in Snowdin Town -not that Papyrus and Sans could really feel the change in climate on account of their lack of skin, but the change in scenery was certainly welcome. Papyrus gazed down at the streams of lava and steam around them, held back by his collar by virtue of Sans's caution and instincts.

"WOWIE. THAT WAS QUICKER THAN I EXPECTED."

"told you i knew a shortcut." Sans said, pulling his brother along towards the path that led to the Hotland apartment building. It was one of the oldest structures in the Underground -aside from the Ruins, but nobody lived there anymore. It still looked pretty modern due to the constant renovations being done, however.

"ARE WE GOING TO WATCH A COMEDY SHOW?" Papyrus anxiously hobbled towards the giant building, trying to keep up with his brother. "OH! ARE WE GOING TO MAKE A RESERVATION AT THE RESTAURANT? I'VE ALWAYS WANTED TO MAKE A RESERVATION."

Sans grinned and opened the door for his brother before following the energetic skeleton through. "even better. we're going to rent a room for the night."

"OH MY GOD!" Papyrus stared at his brother, his jaw agape and his hands curled by his face in excitement. "YOU… YOU MEAN… LIKE A VACATION?"

If Sans wasn't so constantly lethargic, the high that came from putting a smile on Papyrus's face may have made him just as energetic. However, being half-asleep was one of his endearing character traits, so we couldn't very well have that, could we? "yes. just like a vacation."

As Sans spoke to the receptionist, Papyrus grabbed the edge of the reception desk and hoisted himself up so that the top of the desk was just below his chin to better observe the reservation process.

"You know, this place ought to be a resort. There's just more people renting rooms than actually living here nowadays," the receptionist told Sans as they typed something into their computer. "Besides, since when do apartment buildings have restaurants?" They shrugged and concluded with, "Ah, well, I'm not complaining -as long as I'm getting paid." They punched in the last key with gusto and turned around to grab the room key. "Here you go! Let me show you to your room."

* * *

It was only a matter of minutes until Sans was fast asleep on the king-sized bed and Papyrus was sitting in front of the television, eyes glued to the unchanging static. He cast an uncertain glance at his sleeping brother before grabbing his knapsack and a handful of gold. He remembered seeing a snack vendor in the lobby and was starting to feel a bit peckish.

After tiptoeing out into the lobby and leaving Sans with the room key, he walked up to the vendor, a tall monster with a red complexion and anthropomorphic proportions. He was leaning against the wall with his snack cart covering the lower half of his body. Upon seeing Papyrus, he called out in a high pitched drawl. "Heyyyy, chiiiild. Weeelcome to Feeely's Treeets. I'm Feeely. Loooking tooo buuuy sooome dee _eee_ licious treeets?"

Papyrus peered over the top of the cart, looking through the wares. He spotted bags of skeleton-shaped gummy candies in black and red packaging. They sat there almost calling out to him, making his eye-sockets glow with exuberance, and in an ardent, yet slightly startlingly sharp voice, he cried, "THAT ONE! THAT IS THE ONE I CHOOSE!"

"Juuuust oooone?" the vendor asked, a mysterious smile on his face.

Papyrus fidgeted in his boots. The older monster was right. One was way too few and the walk back to the room could potentially be quite tiring; it was best to be prepared. He pulled his knapsack off of his back and dug into his coin pouch, checking the amount of gold that he held. Gingerly, he scooped it all into his hand and put it up on top of the cart. "HOW MANY CAN I BUY WITH THIS?"

The vendor eagerly fingered the coins, counting the gold in his head before pulling out five packets of skeleton gummies and handing them to Papyrus. "Wooow. Luuuucky booooy!"

Papyrus was hardly paying attention as he clung to the packets possessively, afraid to drop them onto the ground. He began to shove them into his bag and thanked the vendor when he had managed to shut the clasp on his precious goodies.

"Beeefore youuu leeeeave!" Papyrus watched Feely expectantly. "A skeeeleton liiiike youuu looooks liiike heeee loo _ooo_ ves aaaadventuuure!"

"YES. HOW DID YOU KNOW? ADVENTURING IS MY FAVORITE THING TO DO… OR. MAYBE. ACTUALLY, PUZZLES ARE MY FAVORITE THING TO DO. BUT ADVENTURING IS AT LEAST A CLOSE SECOND." He decided he really needed to write a list of favorite things so that he didn't get so flustered the next time he talked about them.

Feely's lips curled up in a smile, his three eyes blinking slowly in unison "Peeerfect. Booooy, doooo I haaave an aaaaadveeenture foooor youuu!"

Papyrus trudged along in his too big boots, tailing the older monster as they made their way out of the building and back into the Hotland walkways. He waved to a few monsters he had seen Sans speaking to before. He felt a bit guilty that they all knew his name and he didn't know theirs.

"Staaay clooose, chiiild!" Feely advised, pulling the boy out of harm's way when he wandered too near to a steam vent.

They passed through paths that Papyrus didn't recognize and the farther they went, the less populated these paths were it seemed. He couldn't help but be hit with a slight pang of loneliness, in spite of the presence of his guide; it was like these forlorn paths practically exuded the feeling. It was heavy in the air and Papyrus found himself acutely aware of Sans's absence.

* * *

Sans was startled awake. He wasn't sure how long he'd been out -probably a few hours at most. He rubbed his forehead and looked around the room, trying to spot his brother in his bright blue and magenta shirt in the room. It wasn't a very large room, however, and it didn't take long for him to realize that he had left. There was even a note on the nightstand. It was chicken scratch, so Sans could scarcely make out a few of the words, but he understood the gist of it.

With a sigh, he grumbled. "welp. he can't have gone far…"

He stepped out into the lobby, his slippers softly tapping on the tile floors. There wasn't a soul there aside from the janitor and the receptionist. Come to think of it, wasn't there a snack vendor hanging around here before? Maybe he just went home. Sans walked up to the receptionist and greeted them with a relaxed grin.

"hey, how are you doing? have you seen a little skeleton kid running around here by himself?" he asked. He then held his hand up just below his shoulder. "he's about yea high, wearing a striped shirt, an oversized jacket, and a scarf."

They reached up and scratched the top of their head, the giant index finger on top waving slightly in thought. "I'm not sure. I was on my coffee break up until a quarter of an hour ago. Have you checked the restaurant?"

If Sans had lips, they would have been pressed together in vexation. He quickly thanked the receptionist for their time and dashed off to the left wing of the apartment building where the restaurant was, passing by the host and standing in the doorway, examining the cluster of tables and ignoring the host's polite requests to make a reservation before sitting.

"papyrus?" he half-heartedly called out. He groaned internally. There was likely no reason to check the other floors in the building, but he turned on his heel and headed for the elevator anyway.

His brain barely processed the elevator music in the background as he began to think about where his brother could have gone. He wouldn't have left the building, would he? An image of Papyrus waddling around the CORE with his disproportionately large knapsack weighing him down popped into Sans's head, but he shrugged the thought off like it was a bloodsucking pest. No. He wouldn't go there.

He cleared his mind, watching the floor number on the elevator wall change from zero to one and trying to keep his mind off of the CORE. Absentmindedly, he felt for his cellphone in his pocket, feeling reluctant to take it out.

* * *

 _DING!_

Feely pulled gently on Papyrus's hand, escorting him out of the lift. Just a bit more…

"ARE WE THERE YET?" the boy asked, looking up at Feely with an eager expression on his face that nearly made the man's twisted smile twitch and unfurl.

"Almost," came the reply.

The scenery around them now looked nothing like the familiar Hotland landscape. The lava wasn't present anymore, but it didn't look like they had gone to Waterfall either. They were in an area full of… trees? It was almost like someone had taken Snowdin and forcibly thrust it into autumn. Now, this was truly an adventure Papyrus could appreciate. He thought about taking Sans there; he could almost hear Sans say, in that perpetually sarcastic and light tone, "what a leaf-ly forest" or maybe something like that? Papyrus could never truly emulate his brother -not even in his imagination. Someone like Sans was really one of a kind.

The two came across a large skull blocking their path, but unlike Papyrus's skull, this one seemed to belong to some kind of snake. Staring through the gaping mouth, he could see the rest of the creature's body. However, unlike him, it wasn't moving, which caused a twinge of panic to course through his small body.

"Don't be afraid," Feely told him. Had something changed in him?

"MR. FEELY, WHY ARE WE HERE?" he hesitantly demanded, his feet starting to feel weak and tired. That skeleton gave him the impression that if he stayed there any longer, he'd be just as static.

Feely didn't seem to be paying attention to him. Hand still firmly wrapped around Papyrus's small hand, he brought them closer to the giant skull, their footsteps muffled by the fallen leaves around their boots.

Papyrus looked up and around as they crossed the threshold into the snake's mouth and began walking through its winding body. The shadows of the creature's ribcage made him feel claustrophobic. It was like being in a prison, and on either side of him, the only thing he could see through the white bars was the thick forest of trees so tall, he couldn't even see the tops of them. He pondered the idea of these trees extending even to the human world. Maybe if he climbed one of them, he would find out and they wouldn't need to cross through the barrier to be free.

The path was winding and Papyrus could sense his claustrophobia creeping up on him like cold ice closing in on his heart. He didn't want to feel afraid; the Great Papyrus didn't know fear. He was fearless. He was fearless. Maybe if he said it enough times, it would come true.

At long last, they came upon a large growth of branches, crossing over each other and overlapping to make the entire area impassable. Papyrus was about to declare that it had been a fun adventure and suggest going back up to Hotland when Feely raised one of his crimson hands to the wood. With a small radial motion of his wrist, the barrier began to clear out, the branches slithering away into the shadows like serpents.

Before them now was something that resembled a doorway, which led them into a dim room. The chamber was large, but mainly nondescript. The walls, as far as Papyrus could see, were made of sturdy yet discolored wood, and the floor was covered in dirt and dust. The only thing he noticed was the fact that this chamber also lacked doors.

Upon noticing Papyrus looking up at him expectantly, Feely smiled mysteriously. "Why don't you see if you can solve this puzzle for us?"

The skeleton warily contemplated this. On one hand, puzzles were certainly one of life's greatest pleasures in his own opinion; on the other hand, merely being in this place made him feel that icky emotion that reminded him of fear.

He slipped his hand out of Feely's and approached the wall on the far end of the room. He ran his gloved hands over the wood, feeling for any nonconforming planks -something to give him a clue about how to proceed in this remarkably empty room. Sure enough, his fingers slipped into a small hole in the wood. With as much strength as he could muster with his tiny arms, he tugged on the plank, pulling it away with more ease than he had expected.

Removing the wood completely revealed a small panel hidden beneath the boards and nestled in that panel was a bronze switch, glimmering slightly in the miniscule ray of light provided by the open door on the opposite wall. Casting aside his hesitation, Papyrus reached for the switch and pulled it down.

Immediately, the sound of gears echoed within the walls as a segment of wood, at least three times as tall as him and five times as wide, slid aside. Before Papyrus could look inside, however, he turned around to acknowledge his companion.

"MR. FEELY, LOOK! I DID IT! I-"

But nobody was there.

Feeling his anxiety near its peak, he dashed across the room and through the crisscrossed branches, back into the skeletal corridor.

Feely wouldn't just leave, would he?

He kept running, under miles and miles of the dead snake's ribcage. Was it always this long? Or was his mind playing tricks on him?

He knew Sans was probably worried about him, and guilt as well as terror began to clog up his throat. Whenever he got out of this, he would definitely go hug Sans and apologize for being such a burden, but for now, he had to get home.

He could finally see the skull in the distance and began to pick up the pace, his legs almost leaping out of their joints. He closed in on the entranceway so quickly that he didn't even have time to slow down when he realized the bitter truth.

The snake's jaw was clamped shut, trapping him inside. Did Feely do this? Did he just leave forever? Why would he do that? So many questions filled his mind, and each one came with a sharp sting in his eyes.

Papyrus didn't want to believe it, but he was alone now, and so there, in the dirt and grass, with nobody there to watch, he let himself give in to his fear. His legs buckled beneath him, no longer willing to carry him, and he buried his face into the ground.

"SANS! I'M SO SORRY!" he sobbed. "SANS, PLEASE HURRY UP AND FIND ME!"

* * *

It was with a dejected shove that Sans opened the door to the apartment building. He had searched top-to-bottom and found nothing -no sign of Papyrus. Pushing away the intrusive thoughts that led him to the CORE, he stepped onto the streets of Hotland. His brother had to be there somewhere.

His cell phone bulged in his pocket and, giving in to its call, he reached in to retrieve it. He closed his hand around the plastic and pulled it out in front of his face. He had hoped it wouldn't come to this, but this was about Papyrus; he needed to be sure.

He didn't need to scroll far to find her in his contacts, and once he did, he dialed and placed it where his ear would be.

 _Ring… ring… ring…_

"c'mon. pick up…"

Just then, a feminine voice chirped through the receiver. "H-H-Hello? Sans? Is- Is that you?"

"hey, alphys," he greeted smoothly, betraying none of the concern that held on to his heart like a vice. "i need your help with something."

There was silence on the other end, and who could blame her? She and Sans hadn't exactly been on speaking terms for the last few years. "U-um… S-sure. Come o-over to my place if you like." she stammered.

"i'm on my way," he replied curtly, shutting the phone without giving her a chance to reply. As he rushed, the same thought passed through his mind over and over, with its own voice and its own tone, like a repressed memory resurfacing…

 _THE CORE IS BOTTOMLESS SO TRY NOT TO FALL. IT'S A LONG WAY DOWN IF YOU DO…_

* * *

 ** _This is my first attempt at an Undertale fanfic. I hope it wasn't too out-of-character or contradictory or anything._** ** _Like always, I would appreciate any feedback you could give me._**


	2. S for Snake

The grove was silent save for the sound of small fingers scraping against the dirt and grass. It didn't take very long for Papyrus to untangle the knot that abandonment had made of his mind -it wouldn't have been the first knot he'd ever untied -and with endless possibilities going through his head, only one logical course of action presented itself…

He'd have to go deeper into the serpent's den.

A door locking only from the outside sounded ridiculous since anyone could be locked inside. There was always an opening mechanism inside, so maybe giant snake skulls were no different.

Steeling his resolve, he marched right up to the door he had opened earlier, finally daring to look inside. What he stepped into was what looked like a foyer almost more grand than that of King Asgore himself -not that he'd ever been to visit Asgore -with twin grand helical staircases leading up to the second floor, at the forefront of his vision. It was quite impressive, he had to admit. The walls and fixtures were made of dark wood similar to the wood in the previous room, but much more healthy-looking, and in stark contrast to all that darkness, was the floor, made of white reflective marble; it looked so clean that he probably could have eaten off of it if he wanted to. Thankfully, his common sense managed to persevere throughout the five seconds in which this thought was crossing his mind.

His boots echoed against the walls as he took a few steps forward, and no sooner had he taken those steps than the doors slammed shut behind him. He turned his head to look at the door with dread. He wanted to run towards it and slam his fists against it, demanding its immediate reopening.

 _NO TURNING BACK, PAPYRUS. YOU CAN DO IT._

Keeping his back facing the door, he resumed his solitary walk. Around him, lining the walls on the ground floor, were several doors, four on each side. Each of them had different symbols engraved on them, but they were all too far to make out in the dim lighting. He had no way of knowing what they represented yet, but perhaps he'd find something if he looked around for a bit.

 _ANOTHER PUZZLE?_

He began approaching one of the doors, the first one on his right, and yelped in surprise when he found himself stepping over something small and hard. He kneeled down to pick it up. It was a small metallic figurine, blue in color and flat; the image carved into it was a snake coiled around a rod. He decided to pocket the figure and move on.

The door refused to open when he turned the knob, and upon further examination, he noticed that the symbol he saw earlier was carved into an oddly shaped depression in the door, the inside of which was painted a bright neon green that seemed to glow eerily. He extracted the blue figurine and attempted to place it against the opening. As he had expected, it didn't fit, but he was certain there had to be more of these figures scattered around the grand hall. The hard part of this puzzle, however, was actually finding them. Fortunately, the floor was white; unfortunately, it was also vast.

After a good half hour of searching, he had managed to find what he assumed to be all eight of the door keys in various corners of the upper and lower levels of the foyer; a couple under the staircase and a couple behind the tall pillars holding the second floor of the mansion up, a few hiding between the railings. Each of the figurines was shaped like a different type of snake, and each of them was in a different color: sea blue, green, violet, red, orange, yellow, indigo and fuchsia. They were also smooth to the touch and glossy in the dull light.

Papyrus approached the first door on the right with the pink snake and fidgeted with the figure until it fit. It wasn't necessarily hard to put it in, but his lack of height made it difficult to see where he was pressing the key. Eventually, it sunk into the hole, fitting perfectly, and he heard a muffled click. With that, the door swung open slowly, revealing a small and narrow chamber with barely enough room for him to extend his short arms fully at his side. He braced himself and stepped inside.

The room was much brighter than the foyer. It was as though the very walls were illuminated. At the far end of the room, there was a large pink luminous cube with a luxurious pillow sitting on top, and on that pillow was a figurine made up entirely of small wooden cubes that seemed to resemble a serpent. Uncertain of what to do with the thing, he snatched it and placed it in his backpack.

Upon entering the other seven rooms, Papyrus found similar objects in different shapes, but all made up entirely of cubes. He gathered them all; obviously they must have been important or there would have been no point in opening those doors.

After he had all the wooden figures, he went up the stairs to look for the next door he needed to open. While the second floor seemed large enough that it would have more than one door, there was only one. It was right between the two staircases and was larger than any door Papyrus had ever seen in his entire life. There was a depression in the door shaped like a perfect square, so proportionately small and nondescript that he almost missed it. In the center of that depression was a single cube, affixed solidly; it seemed to be made of the same wood of the eight figures he had collected.

He shrugged his backpack off of his shoulders and set it carefully on the ground. He then began to rummage through, pulling out all the wooden figures. His hands brushed over the plastic wrapping of the gummibones he had bought from Mr. Feely and he felt a pang of hunger slide down his spine and rattle his bones. He gave the bags a cautious look. He only had five and he wasn't certain he'd be able to eat later if he didn't save them.

Shaking his head to snap himself out of it, his attention went back to the puzzle at hand. He held a couple of the pieces together and compared them. They all seemed to be made up of exactly twenty-seven small cubes. It occurred to him that he may have had to figure out a way to make them all fit perfectly into the gap in the door, but with their irregular shapes, it looked to be a nearly impossible task.

He let out a small sigh, fiddling with one of the snake-like figures in his hand. Upon closer inspection, it seemed like the cubes rotated in place; was that the key to solving this puzzle? He could feel the gears in his head kickstart as he tweaked the small cubes. If he could get the pieces to form a larger cube, it would be easy to fill the hole in door.

It only took a couple of minutes for Papyrus to rotate the last cube and the first piece of the larger puzzle was complete. He placed the piece in one of the corners and heard a clicking noise. He tried to pull the piece back out, only to realize that it was now fixed in place.

Knowing exactly what he had to do, he began working on the other seven pieces. As he did, he thought about his predicament. He had to admit that he was somewhat enjoying these small serpent puzzles, though the fact that he was trapped made his enthusiasm lukewarm at best. He couldn't very well sit around and solve puzzles all day when Sans was probably worried sick. He needed to find a way out and as long as he couldn't go back the way he came, the only way to go was forward.

* * *

Alphys alternated between holding her breath in anxiety and letting out long, tired sighs. She could only guess at what Sans wanted from her. The two of them rarely ever spoke and the last time they were on speaking terms was when she found him lurking around her laboratory on her first day of work. He had told her that he stumbled in by accident, giving her a mysterious smile before wandering off deeper into the lab. When she had gone after him to find him, he was nowhere to be seen.

Nowadays, she never spoke to him and she had never seen him in her lab again. She still looked, once in a while, for a hidden door -anywhere Sans could have disappeared to on that strange day, but her efforts proved futile, and eventually she gave up. Now, however, he was coming to her lab to ask for her help. What could he possibly want?

"yo."

"A-Ah!" Alphys yelped, stumbling back into her rolling chair and nearly rolling out of her lab. "Sans. Y-You're here already?" He was standing casually, with his hands behind his back, nearly two feet away from her. She had scarcely put her phone down. How had he gotten here so fast?

"i was in the neighborhood," he replied smoothly, raising one hand to idly scratch his chest. "you look surprised."

Alphys let out a series of nervous chuckles. "Ah, I hadn't expected you to get here so fast."

Sans grinned. "i knew a shortcut." That's what he had told her the first time they had met in her lab before disappearing into thin air.

"C-Can I… help you with something?" she asked, trying not to look like an accident waiting to happen. "You said you needed help?"

"Papyrus is missing," he said, more seriously than she had ever heard him speak. "You're going to help me find him."

"I am?"

"You are."

She bit her lip and felt her tail suddenly grow heavy. "B-But… wouldn't the guards be more helpful? I don't see h-how…"

"i have to make sure of something," he told her. "do you know anything about the core?"

"The CORE?" she asked, unsure of what that had to do with it. Unless… Sans was worried that Papyrus had fallen in. "I didn't create the CORE," she replied uncertainly. "The Royal Scientist before me -"

"Do you know anything about it?" There he went again with that icy tone.

"A bit?"

"a bit?"

"I h-have cameras all around it and I can control its layout from my computer. If you think Papyrus is there then -" She stopped herself before finishing her sentence. "Wait! My cameras! Where did you last see P-Papyrus?"

"the hotland apartment building," he told her, raising his eyebrow… somehow.

"G-Great!" she told him, rushing to her computer with renewed energy. "I-I can l-look… I-I mean… find. I can f-find him using my cameras. All I need to d-do is r-review the footage from earlier today and I can see which way he went. Maybe h-he's not in the C-CORE after all!"

Sans looked tense, but he didn't show any signs of rejecting this idea. It would definitely be a relief if Papyrus had gone somewhere other than the CORE. He stood by as Alphys typed into her computer rapidly before bringing up the footage of the apartment building lobby from earlier. It was empty save for a snack vendor standing by the door. After a minute, Papyrus came into view, making a beeline for the vendor. Sans's eye sockets seemed to darken as he watched the man grab Papyrus's hand and walk off.

"W-Well… he's not in the CORE, I guess! S-So he's safe, right?" Alphys said, but Sans didn't speak.

He reached for the computer interface and changed the surveillance camera view. This one showed one of the paths in Hotland. When the pair reached a certain elevator, they were no longer on any of Alphys's cameras, but Sans didn't need a surveillance camera to know exactly where they were headed.

"I-I didn't know we had an elevator there," Alphys remarked, leaning into the screen. "Where did that come from?"

* * *

"WOWIE! I DID IT!" Papyrus said to nobody in particular, looking at the seven perfect cubes on the ground in front of him. Wasting no time, he grabbed them two at a time and began to tile them in the hole, around the center cube. When he was done, he stared at the door expectantly, only for his excitement to die down when nothing happened. He tugged at the large door, but his tiny bones could not make the door budge.

He sighed and scrutinized the door once more. Perhaps he had done something wrong. His eyes ran across the surfaces of the cubes and noticed that a couple of them had tiny glowing runes in the center, each perhaps, signifying the color of the room they had been found in. With a frown, he tried pulling out one of the non-glowing cubes. It fell out at his touch, almost as though propelled by a spring mechanism. He made sure to catch it before it hit the ground. Rotating the object in his hand, he searched for a similar rune to the ones he saw and found it very easily. He reinserted the cube, leaving the rune facing forward, and heard a clicking sound followed by a dull glow.

Then Papyrus's next course of action became clear to him. He set to work on adjusting the cubes' orientations. When he was finished, there were a set of nine runes on the door before him. Their colors began to change in unison from red to blue to violet -rotating between each of the nine colors until they all flashed a bright white. Before he could react, they all went dim and he heard a loud _clank_.

It was then that he was completely certain he had done it. The door was open and he could finally proceed to the next chamber -or maybe even leave if he was lucky. He watched the door with bated breath as it slowly, but surely, began to rise into the ceiling. He couldn't hold the sigh of relief that slipped past his clamped jawbones.

Past the door was a very bright room; it was quite refreshing compared to the previous rooms he was in, but also quite small. The tiles on the floor were bright and a random multicolored mess. The entire room was five tiles wide and six tiles long. It almost resembled a puzzle he had seen in a book once, so he was tentative about going forward. Of course, the one in the book had clear instructions for him to follow, but this room did not.

Taking in a deep breath, he stepped onto the first tile, which was colored pink. Nothing happened. He let out a nervous chuckle and adjusted the straps of his backpack. All this anxiety was making him hungry, but he wouldn't give into his hunger yet.

There were five tiles around him: one red, two yellow, one blue, and one green. The ones directly adjacent to him were green, red, and blue. He tried going directly forward to the red tile, only to find himself blocked by an invisible barrier. The blue one to his left reminded him of water and he did not wish to get his boots wet, so he elected to save that for last. All that was left was the green tile. He took another hesitant step to his right and let out the breath he was holding when nothing happened.

His next step also made him cautious. There were also five tiles around him now: the pink one he had just come from, the red one in his top left corner, the yellow one right in front of him, a blue one to his left, and finally an orange one in the top right corner. He can hear a low buzzing coming from the yellow tile, and thus decides to move to the left again. However, he doesn't bother to exercise caution as he does, so his boot sinks into the tile, and along with it, his entire leg; the rest of his body soon follows.

He was right. The blue tile was definitely water, although it was much deeper than he had anticipated, and not all of it was water. It was almost as though only the first couple of inches were water and the rest empty air. His pelvic bone soon hit a hard, wet surface and he began sliding through the darkness with no way to slow himself down.

The trip down the long slide seemed to take ages, and after the initial shock wore off, he found himself wondering who had even made such a long slide. Perhaps it was an overly excitable child, or simply a monster who was very enthusiastic about slides. Whatever the case, he could definitely say he was in the slide for a good ten minutes, maybe even longer, before he could see the light again.

The second he could see again, he was thrust into a pool of water. Thankfully, he did not have lungs and thus had no need for oxygen, or else being submerged would have been rather uncomfortable indeed. It took him a moment to gather his bearings and swim up to the top of the pool, and when he did, he finally got a good look at his new surroundings.

He was in Snowdin. Or at least, it looked like he was in Snowdin. It wasn't any part of Snowdin he'd ever seen, but it was the only place in the Underground with snow. There were trees all around him, so it was not quite clear where he was meant to go.

As he climbed out of the pool, he noticed one of the trees in the clearing had a note pinned to it. He scrambled over to it and scanned the words on the page.

 _THE COLORED TILE PUZZLE_

 _Pink does nothing to you. Please do not hesitate to step on it._

 _Red is impassible. Please do not try to pass._

 _Yellow is electricity. Stepping on a yellow tile will be quite unpleasant._

 _Green means you will have to fight another monster. I am only too sorry for this._

 _Orange will make you orange scented. I'm not quite sure why we even have orange tiles._

 _Purple is slippery and will make you slide to the next tile. You will also be lemon scented. I don't fancy lemons very much._

 _Blue tiles are water. They're pretty harmless. Unless you smell like oranges. And it has been scientifically proven that piranhas enjoy the taste of oranges very much. However they don't like lemons at all. So if you smell like lemons, you should be fine._

 _It should be noted, that I am not a piranha. Just putting that out there._

 _If a blue tile is next to a yellow tile, you will be electrified._

 _Please have fun and stay safe._

 _-S_

Papyrus frowned. He definitely could have used this note before he plummeted. Now it was practically useless unless he encountered another colored tile puzzle. He then caught sight of another note hastily pinned to the tree in the exact same place as the other one.

"THIS WASN'T HERE BEFORE…" he mumbled, eyeing the paper suspiciously. He picked it up and read it cautiously.

 _To whom it may concern,_

 _It has come to my attention that perhaps the previous puzzle was a bit unfair. I am really sorry for this. I have prepared another puzzle for you just beyond these trees. Just go straight ahead. I do very sincerely apologize for the inconvenience. Please help yourself to the pool. The water may be a bit cold, but something tells me that won't matter to you._

 _-S_

Papyrus felt a chill in his bones, which was odd since he was a skeleton and couldn't feel the weather. This mysterious "S", the author of these letters… who were they? _S_? _S for who_? _S for Sans_? Were they a friend of Mr. Feely's? And where _was_ Mr. Feely anyway? It was strange that he hadn't come back yet. Maybe Papyrus shouldn't have gone ahead and solved those puzzles. What if Mr. Feely simply left to go get something really quickly and by going ahead, Papyrus had lost him?

He shook his head and took one last look around the clearing before leaving. The slide he had come from was actually quite frightening now that he was getting a good look at it. It was coiled around in wide arches and looked like a giant snake. The opening at the bottom was the snake's mouth, hanging wide open, with its fangs protruding menacingly from the top of its jaw.

He shuddered and turned around, going through the trees in the exact direction the note mentioned. He hoped that after all these puzzles, he would finally find Mr. Feely again and tell him to to take him home again. Maybe Sans would be on the other side of the puzzles. Sans liked practical jokes, but this was a bad joke. If Sans were actually behind this, he'd have to scold him later.

* * *

Sans and Alphys stepped out of the elevator and into a peaceful yet morose forest. There were leaves on the ground and right in front of them was what looked like the gaping jaw bones of an enormous serpent.

Alphys let out an audible gasp and faltered in her step. It was unlike anything she had ever seen. Alphys knew of animals on the surface who, rather than fade completely upon death, left skeletons in their wake. The only skeletons she knew personally, however, were Sans and Papyrus, and they were magical skeletons. She doubts either of them ever had flesh on their bones like surface animals.

"I-I-I…" she was having trouble finding the words to say, but Sans seemed to know exactly what she was thinking.

"you didn't know a place like this existed in the underground?"

Alphys had to admit. She liked Sans more when he was making puns and putting whoopie cushions on people's seats. "You already knew about this place?" Why did Sans have to get more and more mysterious every time she spoke to him? She was having enough trouble being in his presence as it was.

"unfortunately," he replied.

"W-What is it?"

Sans turned his head to face her, a faint azure glowing in one of his eye sockets. "Alphys, listen closely, because I'm only going to tell you this once." She nodded curtly, feeling like spiders were crawling up and down her body, just beneath her scales. "Go back to your lab

"W-W-What?"

"this place is a doorway to another world."

"A-Another…"

"every monster living past this point is already dead."

Alphys's heart skipped a beat. "Living _and_ dead? But that's impossible, isn't it? O-Once you're… d-d-dead… You can't c-c-come back!"

Sans turned away from her and took a couple of steps towards the snake's skull. "not if you have determination."

"B-but there's no way for a monster to have DETERMINATION unless… you…"

"Alphys, go back to your lab."

For moment, she really, _truly_ wanted to go back. It would have been so much easier to just cut her losses and pretend this entire day had never happened, but in spite of her apprehension, the entire notion of a place full of monsters who had come back from the dead filled her with a sense of sick curiosity. A monster with DETERMINATION? This was groundbreaking.

"No." She couldn't even believe the voice was hers, and apparently, neither could Sans, as for a moment, he dropped the serious expression in favor of a more puzzled one. He turned around to face her again.

"what?"

"I said 'N-N-No'!" she winced when her voice lost the strength it had before. "Papyrus is in t-t-trouble. Y-Y-You w-won't… I w-w-won't let you do this alone!" She tried to grin, only for it to come out awkward and halfhearted.

For a moment, Sans was silent. Then he nodded slowly, easing the tension in Alphys's chest. "welp," he started, waving one hand at her, while the other sat in his pocket. "let's get going then."

* * *

 ** _I must really apologize for being a late updater. This summer is suuuper hectic for me since I'm getting ready to move to another country :O_**  
 ** _Anyway, this chapter may not be as eventful as the previous one, but I hope you enjoy it nonetheless._**  
 ** _It's a bit longer than the previous one, though, so I hope that makes up for it :D_**


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